1. Department of Plant Biology, University of Minnesota, St. Paul, Minnesota 55108‐1095 USA
2. University Imaging Centers, University of Minnesota, St. Paul, Minnesota 55108‐1095 USA
3. School of Life Sciences, Arizona State University, Tempe, Arizona 85287 USA
4. Department of Botany, The Zamorin's Guruvayurappan College, Calicut, Kerala 673014 India